In a traditional municipal infrastructure, a sewer system includes, among other elements, a network of manholes interconnected by a series of lateral pipes. Recently, in Europe, North America and elsewhere, regulations require not only inspecting municipal pipes, but also documenting them with respect to the depth and diameter of the manhole, and the number and size of lateral pipes extending from the manholes. Measuring the depth and diameter of a manhole is a relatively easy and straightforward operation. The worker simply removes the manhole cover, measures the diameter of the opening, and lowers a measuring tape down the manhole to determine its depth. Measuring lateral pipes, however, tends to be more difficult. Traditionally, a person would have to be lowered or climb down into the manhole and measure the opening of the lateral pipe at the manhole with a tape measurer or similar instrument.
This approach has a number of drawbacks. First, climbing into a manhole tends to be dangerous as sewer gases and other toxic fumes pose a serious health threat, and can be deadly if proper precautions are not taken. Additionally, climbing into a confined space containing sewage is obviously objectionable. Furthermore, attempting to measure the laterals in this way tends to be unreliable. Specifically, frequently the lateral opening at the manhole is corrupted to the point that it does not provide a reliable indication of the diameter of the pipe. This corruption may be a result of, for example, cracking or damage at the seam between the manhole and the lateral, a repair job using a bulky patch, or just the seam in general that distorts the opening to the lateral such that measuring the opening does not provide a reliable indication of the actual diameter of the lateral pipe further down. Finally, physically measuring the opening of the lateral may be impractical because lateral pipes are often at the bottom of the manhole or underwater, making observations of a tape measurer or other measuring device difficult if not impossible. Therefore, measuring the opening of a lateral at the manhole junction tends to be dangerous and inconvenient, and frequently provides an unreliable indication of the lateral pipe's diameter.
Therefore, applicant has identified the need to be able to measure lateral pipes reliably without entering a manhole. The present invention fulfills this need, among others.